JP4901739B2 - Optical pickup and optical information device - Google Patents

Description

  The present invention relates to an optical information apparatus that optically records and reproduces information, an optical pickup used in the optical information apparatus, and an objective lens unit. The present invention also relates to an application device equipped with an optical information device.

  An optical disk is widely used as an information recording medium capable of recording a large amount of information, and an optical disk with higher recording density has been developed with the advance of technology.

  The first popularized optical disc was the compact disc (CD), and then the digital versatile disc (DVD). Since a DVD can record information at a recording density about six times that of a CD, a large amount of data can be recorded on a single DVD. For this reason, it is particularly used for recording video information with a large amount of information. In recent years, optical discs capable of recording information at higher recording densities, such as HD-DVDs and Blu-ray discs (BD), have been developed, and in particular, have begun to be used for recording high-definition video.

  As various optical discs are developed, compatibility of optical disc apparatuses becomes important. In consideration of user convenience, the optical disc apparatus preferably supports a plurality of optical discs.

As an optical pickup for an optical disc apparatus corresponding to a plurality of optical discs having different recording densities, for example, as shown in Patent Documents 1 to 3, an optical pickup provided with a plurality of objective lenses has been proposed. Such conventional optical pickups mainly correspond to CDs and DVDs.
Japanese Patent Laid-Open No. 10-11765 Japanese Patent Laid-Open No. 11-120588 JP 2002-245650 A

  However, when the inventors of the present invention have studied an optical disc apparatus compatible with an optical disc capable of recording information at a higher recording density, such as HD-DVD and BD, and a conventional CD or DVD, the following has been studied. It became clear that there was a problem.

  For example, in an optical pickup including two objective lenses, the two objective lenses are supported by a common objective lens holder, and the objective lens holder is driven by one objective lens actuator.

  For this reason, the two objective lenses with respect to the objective lens holder need to be fixed to the objective lens holder in an optimal alignment with the optical axis in the optical system using the respective objective lenses. For this purpose, for example, Patent Document 1 fixes one objective lens to a tilt holder, adjusts and fixes the tilt of the tilt holder with respect to the objective lens holder with an adjusting screw, and then tilts the holder and the objective lens holder. Are fixed with an adhesive.

  However, in this structure, it is necessary to fix the tilt holder once with the adjusting screw, and the position adjustment is troublesome. In addition, the size of the aperture with respect to the objective lens changes due to the tilt of the tilt holder, and there is a problem that a desired numerical aperture (NA) cannot be secured.

  Further, in an optical disc such as HD-DVD or BD, in order to achieve a high recording density, it is necessary to use an objective lens having a large numerical aperture (NA) to reduce the light spot for recording and reproduction. For this reason, it is necessary to form a large through hole in the lens holder for fixing the objective lens.

  Since such a lens holder has a large through hole, the rigidity is low, and the lens holder is likely to resonate at a predetermined frequency. As a result of investigations by the present inventor, it has been found that this resonance affects the operation of the objective lens actuator that drives the objective lens holder, and it may be difficult to perform highly accurate objective lens control.

  Further, the control accuracy differs in recording / reproducing operations for a plurality of optical disks having different recording densities. In general, high control accuracy is not required for recording / reproduction of an optical disc having a low recording density, but since the recording density is low, the moving range of the objective lens is required to be large. On the other hand, in the recording / reproduction of an optical disc having a high recording density, high control accuracy is required, but the movement range of the objective lens may be narrow.

  However, when a plurality of objective lenses are supported by the objective lens holder, it is generally difficult to satisfy such different specifications because there is one actuator that drives the objective lens holder.

  SUMMARY OF THE INVENTION An object of the present invention is to solve at least one of the problems of the prior art and to provide an optical pickup and an optical information device provided with a plurality of objective lenses.

  The objective lens unit of the present invention includes a first objective lens and a first lens holder that supports the first objective lens, and the first lens holder is made of a material that transmits ultraviolet rays.

  In a preferred embodiment, the first lens holder has first and second openings, a through-hole through which light incident on the first objective lens passes, and a circumferential direction in the through-hole. The first objective lens is supported so as to close the first opening, and the opening restriction portion extends from the second opening to the first opening. The light incident on the aperture limiting portion is guided in a direction away from the optical axis of the first objective lens.

  In a preferred embodiment, the opening limiting portion has a first ring-shaped slope inclined with respect to the inner surface of the through hole so as to face the first opening.

  In a preferred embodiment, the opening limiting portion has a second ring-shaped inclined surface inclined with respect to the inner surface of the through hole so as to face the second opening side.

  In a preferred embodiment, the opening limiting portion includes a first ring-shaped inclined surface inclined with respect to the inner surface of the through hole so as to face the first opening side, and the second opening side. And a second ring-shaped inclined surface inclined with respect to the inner surface of the through-hole.

  In a preferred embodiment, the angle formed between the light incident on the second ring-shaped slope and the normal line of the second ring-shaped slope is A1, and the light emitted from the second ring-shaped slope is An angle formed by the normal line with the second ring-shaped slope is A2, and an angle formed by the light incident on the second ring-shaped slope and the normal line of the first ring-shaped slope is A3, When the refractive index of the aperture limiting portion is n, the relationship of sin (A1) = n · sin (A2) and n · sin (A3 + (A1−A2))> 1 is satisfied.

  In a preferred embodiment, the ring-shaped slope has two discontinuous ring-shaped slopes arranged concentrically.

  In a preferred embodiment, the opening restricting portion has a shape constituting a part of a concave lens having an axis coinciding with the central axis of the through hole.

  In a preferred embodiment, a cross section passing through the central axis of the through hole of the opening limiting portion is a part of an ellipse protruding toward the central axis.

  In a preferred embodiment, the opening limiting portion has a diffraction grating provided on the first opening side.

  In a preferred embodiment, the aperture limiting portion has a scattering surface that scatters light rays provided on the first aperture side.

  In a preferred embodiment, the opening limiting portion has a shielding surface that shields a light beam provided on the first opening side.

  The optical pickup of the present invention includes a first light source, an objective lens unit defined in any of the above, a support that holds the objective lens unit, an actuator that drives the support, and a first photodetector. The light emitted from the light source is condensed on the data recording surface of the optical disc by the first objective lens of the objective lens unit, and the light reflected on the data recording surface is converted into an electrical signal by the photodetector. .

  In a preferred embodiment, a first lens holder of the objective lens unit is bonded to the support with an ultraviolet curable resin.

  In a preferred embodiment, the optical pickup further includes a second objective lens and a second light source that do not share an optical axis with an optical system configured by the objective lens unit, and the support supports a second objective lens that supports the second objective lens. 2 lens holder.

  In a preferred embodiment, an interval between the optical axis of the first objective lens and the optical axis of the second objective lens is 5 mm or less.

  In a preferred embodiment, an interval between the optical axis of the first objective lens and the optical axis of the second objective lens is 2.5 mm or more and 5 mm or less.

  In a preferred embodiment, the first objective lens and the second objective lens are arranged so as to be positioned in a tracking direction of the optical disc.

  In a preferred embodiment, the first objective lens and the second objective lens are arranged so as to be positioned in a direction perpendicular to a tracking direction of the optical disc.

  In a preferred embodiment, the first lens holder has a flat side surface at a position close to the second objective lens.

  In a preferred embodiment, the first lens holder has a flat side surface outside the optical disc.

  In a preferred embodiment, the first objective lens is used for condensing light having a longer wavelength than the second objective lens.

  In a preferred embodiment, the first lens holder has a notch at a position symmetrical to the flat side surface with the optical axis of the first objective lens as a center.

  In a preferred embodiment, the apparatus further comprises a protrusion protruding from the first lens holder and the second lens holder than the first objective lens and the second objective lens, and the protrusion is other than the outer peripheral side of the optical disc. It is provided in the area.

  The optical pickup of the present invention includes a first light source that emits light of a first wavelength, a first objective lens that condenses the light emitted from the first light source toward a recording surface of a first optical disc, and the first A first detector that receives reflected light of the light collected on the recording surface of the optical disc and outputs a detection signal; a second light source that emits light having a second wavelength shorter than the first wavelength; and the second light source. A second objective lens for condensing the light emitted from the recording surface of the second optical disc, and a second detection for receiving a reflected light of the light condensed on the recording surface of the second optical disc and outputting a detection signal The focus detection range of the focus error signal generated based on the detection signal of the first detector is larger than the focus detection range of the focus error signal generated based on the detection signal of the second detector. It is getting wider.

  In a preferred embodiment, the optical pickup includes a first collimating lens for reducing the divergence of the light emitted from the first light source, and a second for reducing the divergence of the light emitted from the second light source. A first magnification obtained by dividing the focal length of the first collimating lens by the focal length of the first objective lens, and the focal length of the second collimating lens is the second objective lens. Is smaller than the second magnification obtained by dividing by the focal length of.

  In a preferred embodiment, the focal length of the first objective lens is longer than the focal length of the second objective lens.

  In a preferred embodiment, the optical pickup includes a first collimating lens for reducing the divergence of the light emitted from the first light source, and a second for reducing the divergence of the light emitted from the second light source. A collimating lens, and the focal length of the first collimating lens is shorter than the focal length of the second collimating lens.

  The optical information device of the present invention controls the optical pickup based on a signal obtained from at least the first optical detector of the optical pickup, a motor for rotating and driving an optical disc defined in any one of the above. And an electric circuit.

  A computer according to the present invention includes the optical information device.

  An optical disc player of the present invention includes the optical information device.

  The car navigation system of the present invention includes the optical information device.

  An optical disk recorder of the present invention includes the optical information device.

  An optical disk server of the present invention includes the optical information device.

  The vehicle of this invention is provided with the said optical information apparatus.

  The optical pickup assembly method of the present invention is the optical pickup assembly method described above, wherein coma aberration on the recording surface of the optical disc when the light beam from the second light source is condensed by the second objective lens. In the first step of adjusting the inclination of the entire first lens holder so as to be minimized, and in the state in which the inclination of the entire first lens holder adjusted in the first step is maintained, the second objective lens performs the first step. A second step of adjusting an inclination of the objective lens unit with respect to the first lens holder so that coma aberration on the recording surface of the optical disc is minimized when a light beam from one light source is condensed; Include.

  In a preferred embodiment, the optical pickup further includes a third light source condensed by a second objective lens, and condenses the light beam from the third light source by the second objective lens after the second step. In this case, the method further includes a third step of adjusting the position of the third light source in the direction perpendicular to the optical axis of the light beam so that the coma aberration on the recording surface of the optical disk is minimized.

  An objective lens driving device according to the present invention includes a movable body including a first objective lens and a second objective lens for converging a light beam on an optical disc, and a support that supports the first objective lens and the second objective lens. In the objective lens driving device, the distance between the optical axes of the first objective lens and the second objective lens is 5 mm or less.

  In a preferred embodiment, the distance between the optical axes of the first objective lens and the second objective lens is 2.5 mm or more and 5 mm or less.

  The objective lens driving device of the present invention supports a first objective lens and a second objective lens for converging a light beam on an optical disc, a first lens holder for supporting the first objective lens, and the second objective lens. An objective lens driving device including a movable body including a second lens holder, wherein the first lens holder is fixed to the second lens holder, and the first lens holder is attached to the second lens holder. A flat side surface is provided at a position close to the supported second objective lens.

  In a preferred embodiment, the first lens holder has the flat side surface outside the optical disc.

  In a preferred embodiment, the first objective lens is used for condensing light having a longer wavelength than the second objective lens.

  In a preferred embodiment, the first lens holder has a notch at a position symmetrical to the flat side surface with the optical axis of the first objective lens as a center.

  In a preferred embodiment, the objective lens driving device further includes a protrusion protruding from the first lens holder and the second lens holder than the first objective lens and the second objective lens, and the opening restriction portion is , Provided in a region other than the outer peripheral side of the optical disc.

  According to the objective lens unit of the present invention, since the objective lens unit is formed of a material that transmits ultraviolet rays, when the objective lens unit is fixed to the support, after the inclination of the objective lens lens unit is adjusted, an ultraviolet curable resin is used. The objective lens unit can be fixed. For this reason, it is possible to easily adjust the position and inclination of the objective lens unit.

  In addition, since the objective lens unit includes the aperture limiting portion, the light diameter of the light beam incident on the objective lens from the outside can be always adjusted to be constant by the aperture limiting portion even if the inclination of the objective lens unit with respect to the support is adjusted. .

  Further, according to the optical pickup of the present invention, since the distance between the optical axes of the two objective lenses is 5 mm or less, it is possible to suppress the deterioration of the servo control performance due to the resonance of the lens holder and realize stable control. it can.

  In addition, since the first lens holder has a flat side surface at a position close to the second objective lens, the distance between the two objective lenses can be reduced, and the distance between the optical axes of the two objective lenses can be shortened. be able to.

(First embodiment)
A first embodiment of an optical pickup according to the present invention will be described below. 1 and 2 are a schematic side view and perspective view of the optical pickup 101. FIG.

  In FIG. 1, direction T is the tracking direction, and direction F is the focusing direction. The direction Y is a direction perpendicular to the tracking direction. The optical pickup 101 is arranged so that these directions coincide with the tracking direction, the focusing direction, and the direction perpendicular to the tracking direction of the optical information apparatus (optical disk apparatus). However, it is also possible to arrange the direction Y and the direction T so that they coincide with the tracking direction of the optical information device and the direction perpendicular thereto.

  The optical pickup 101 can perform at least one of recording and reproduction on the optical disks 32, 35, and 46 having three different recording densities. The optical disks 32, 35, and 46 are, for example, DVD, BD, and CD.

  The optical pickup 101 includes a light source 31 and an objective lens 34 in order to perform at least one of recording and reproduction with respect to the optical disc 35 having the highest recording density.

  The light source 31 emits light having the shortest wavelength (for example, blue). The light emitted from the light source 31 is linearly polarized light in a predetermined direction. The polarization beam splitter 1032 guides the light emitted from the light source 31 to the collimating lens 33. The polarization beam splitter 1032 strongly reflects linearly polarized light in the direction of light emitted from the light source 31, and transmits linearly polarized light in a direction perpendicular to the linearly polarized light at a high rate. The combination of the quarter wavelength plate 48 and the polarization beam splitter 1032 described below can also provide an effect of improving the light use efficiency.

  The collimating lens 33 converts the convergence state so that the light beam 56 emitted from the light source 31 becomes substantially parallel light. The prism 60 has an inclined surface 60 a and reflects the light beam 56 transmitted through the collimating lens 33 in a direction perpendicular to the optical disk 35. The objective lens 34 converges the light beam 56 on the recording surface of the optical disk 35. The light beam reflected by the recording surface of the optical disk 35 follows the original optical path in the reverse direction, is branched in a direction different from the light source 31 by a branching means such as a polarization beam splitter 1032, and enters the photodetector 36. The photodetector 36 photoelectrically converts incident light and outputs an electric signal for obtaining an information signal and a servo signal (a focus error signal for focusing control and a tracking signal for tracking control).

  Here, by providing the quarter-wave plate 48 between the polarizing beam splitter 1032 and the objective lens 34, linearly polarized light reflected by the polarizing beam splitter 1032 can be converted into circularly polarized light. When the light beam 56 that has been circularly polarized in the opposite direction due to reflection on the recording surface of the optical disk 35 is incident on the quarter-wave plate 48 again, it is converted into linearly polarized light in a direction orthogonal to the original direction. Therefore, the light is transmitted through the polarizing beam splitter 1032 at a high rate, and the light use efficiency is improved.

  An astigmatism generation element 50 such as a cylindrical lens or a toric lens is disposed between the polarization beam splitter 1032 and the photodetector 36, and a four-divided light detection region (not shown) is provided in the photodetector 36. Also good. By adopting such a configuration and receiving light with astigmatism added by the astigmatism generating element 50, a focus error signal by the astigmatism method can be detected. Further, if a lens power having a condensing and diffusing power to the astigmatism generating element 50 is added, the astigmatism generating element 50 can be moved in the optical axis direction, and the offset adjustment of the focus error signal can be realized. Furthermore, a diffractive optical element (DOE) 51 is disposed between the polarization beam splitter 1032 and the photodetector 36, whereby a stable tracking signal of one beam system can be obtained.

  The optical pickup 101 includes a light source 37a and an objective lens 41. The light source 37 a is housed in the integrated unit 37 and emits light having a wavelength longer than that of the light source 31 (for example, red). The collimating lens 39 converts the convergence state of the light beam 57 so that the light beam 57 emitted from the light source 37a becomes substantially parallel light. The light beam 57 transmitted through the collimator lens 39 is reflected in a direction perpendicular to the optical disk 32 by a slope 60 b different from the slope 60 a of the prism 60.

  The objective lens 41 converges the light beam 57 on the recording surface of the optical disc 32. The light beam reflected by the recording surface of the optical disk 32 follows the original optical path in the reverse direction and is branched in a direction different from the first by a branching means such as a polarization hologram 40, and a photodetector (not shown) of the integrated unit 37 is shown. And photoelectrically converted. Thereby, an electric signal for obtaining an information signal and a servo signal (a focus error signal for focusing control and a tracking signal for tracking control) is output. By using the integrated unit 37 in which the photodetector and the light source 37a are built, the optical pickup can be reduced in size and thickness, and the operation of the optical pickup can be stabilized.

  The optical pickup 101 further includes a light source 43a. The light source 43a is housed in the integrated unit 43 and emits light having the longest wavelength (for example, red). The collimating lens 39 converts the convergence state of the light beam 57 so that the light beam 58 emitted from the light source 43a becomes substantially parallel light. The light beam 58 transmitted through the collimating lens 39 is reflected in a direction perpendicular to the optical disk 46 by the inclined surface 60 b of the prism 60.

  The objective lens 41 converges the light beam 58 on the recording surface of the optical disk 46. The light beam 58 reflected by the recording surface of the optical disk 46 follows the original optical path in the opposite direction, and is branched in a direction different from the light source 43a by a branching means such as the hologram 43b, and is not shown in the integrated unit 43. It enters the photodetector and is photoelectrically converted. Thereby, an electric signal for obtaining an information signal and a servo signal (a focus error signal for focusing control and a tracking signal for tracking control) is output. By using the integrated unit 43 including the photodetector and the light source 43a, the optical pickup can be reduced in size and thickness, and the operation of the optical pickup can be stabilized.

  As shown in FIGS. 1 and 2, the optical pickup 101 includes a beam splitter 38 having a dichroic film for multiplexing or branching light emitted from the light source 37a and the light source 43a. A part of the light emitted from the light source 43 a is reflected by the beam splitter 38 and guided to the photodetector 54. The remaining light passes through the collimating lens 39. Further, a part of the reflected light from the optical disk 46 is transmitted and guided to the integrated unit 43. The beam splitter 38 totally reflects the light from the light source 37a.

  The cross section of the prism 60 is a triangle, but the apex (ridge as viewed as the entire prism) may be chamfered to prevent chipping. Including this case, the prism 60 has an approximately triangular cross section.

  In this embodiment, the optical pickup 101 corresponds to three types of optical discs and includes three light sources. However, in order to realize an optical information device corresponding to two types of optical discs, the optical pickup 101 may include a light source 43a or a light source. Any one of 37a and the light source 31 may be provided.

  The optical pickup 101 includes an objective lens driving device 45, and the objective lens 34 and the objective lens 41 are disposed at predetermined positions in the objective lens driving device 45. It is desirable that the objective lens 34 and the objective lens 41 are arranged side by side in the direction Y, that is, the direction in which the track groove of the optical disk extends or the direction perpendicular to the tracking direction. Accordingly, when the objective lens 34 or the objective lens 41 accesses the outermost or innermost circumference of the optical discs 32, 35, or 46, the objective lens 41 or the objective lens 34 that is not used removes the optical discs 32, 35, or 46. Interference with the rotating motor and the exterior of the optical information device can be prevented.

  The objective lens driving device (objective lens actuator) 45 moves the objective lens 34 and the objective lens 41 in both the focusing direction F orthogonal to the recording surfaces of the optical disks 35, 32, and 46 and the tracking direction T of the optical disk. The condensing state of the light spot used for recording and reproduction of 35 and 46 can be adjusted, and the position of the light spot can be moved in the tracking direction.

  FIG. 3 shows a cross section of the movable part of the objective lens driving device 45. The movable portion supports and fixes the objective lens 34 and the objective lens 41, and the objective lens 34 and the objective lens are moved by moving the movable portion in the focusing direction and the tracking direction by a driving mechanism such as a coil and a magnet (not shown). 41 is moved in the focusing direction and the tracking direction.

  After both the objective lens 34 and the objective lens 41 are fixed to the movable part, the directions of the objective lens 34 and the objective lens 41 cannot be adjusted independently. For this reason, the direction of the optical axis of the objective lens 41 with respect to the optical axis of the objective lens 34 needs to be adjusted in advance.

  In the present embodiment, the movable portion includes the objective lens 34, the lens holder 1, and the objective lens unit 10 on which the objective lens 41 is supported, and the first lens holder 1 to which the objective lens 34 is fixed. The direction of the objective lens unit 10 can be adjusted. For this purpose, the objective lens unit 10 has a lens holder 2. The lens holder 2 supports and fixes the objective lens 41. Further, the lens holder 2 has a bottom portion 2r formed of a curved surface, and is supported and fixed so that the bottom portion 2r of the lens holder 2 is in contact with the concave portion 1r formed of the curved surface of the lens holder 1.

  Since the bottom 2r of the lens holder 2 is formed of a curved surface, the lens holder 2 and the lens holder 1 can be fixed after adjusting the inclination of the lens holder 2 in the recess 1r of the lens holder 1.

  The adjustment of the inclination of the lens holder 2 is performed by the following procedure, for example. First, when the light beam 56 reflected by the inclined surface 60a in FIG. 1 is condensed by the objective lens 34, the coma aberration is minimized, or the convergence spot is most symmetrical with respect to the optical axis. The inclination of the lens holder 1 is adjusted so that This adjustment is performed by adjusting the position of the lens holder 1 in the movable portion or by adjusting the inclination of the objective lens driving device 45 with respect to the optical axis of the light beam 56 reflected by the inclined surface 60a.

  Next, in this state, the inclination of the lens holder 2 to which the objective lens 41 is fixed with respect to the lens holder 1 is adjusted. When the light beam 57 reflected by the inclined surface 60b is collected by the objective lens 41, the coma aberration is minimized, or the convergence spot is made to have the most symmetric shape with respect to the optical axis. Further, when the position of the light source 43a is adjusted in the direction perpendicular to the optical axis and the light beam 58 reflected by the inclined surface 60b is collected by the objective lens 41, the coma aberration is minimized or the convergence spot. To be the most symmetric with respect to the optical axis.

  According to the conventional technique disclosed in Patent Document 1, the inclinations of the two objective lenses are determined so that the optical axes of the two objective lenses are parallel to each other. However, according to this method, coma aberration caused by manufacturing errors of the objective lens and coma aberration of the light beam due to manufacturing errors of other optical components remain, and the convergent beam is distorted.

  On the other hand, with the adjustment method of the present embodiment, coma aberration can be reduced comprehensively, or the shape of the convergent beam can be optimized. For this reason, it is possible to realize an optical pickup capable of exhibiting good recording and reproducing performance for a plurality of different types of optical disks.

  After adjusting the inclination of the lens holder 2 with respect to the lens holder 1 in this way, the lens holder 2 is fixed to the lens holder 1 using an adhesive 22 as shown in FIG. In general, thermosetting adhesives are widely used for bonding electronic components. However, in order to use a thermosetting adhesive, it is necessary to prepare a high-temperature tank, and an extra manufacturing facility is required. Moreover, when using the adhesive which hardens | cures with time passage, it is desirable for hardening time to be short from a viewpoint of manufacturing time shortening. However, when the curing time is short, there is a problem that the curing of the adhesive proceeds while adjusting the tilt of the lens holder 2 and is difficult to adjust.

  In the present embodiment, it is preferable to use an ultraviolet curable resin as the adhesive 22 in consideration of these points. The adhesive 22 is also preferably applied to the gap between the lens holder 1 and the lens holder 2 so that the lens holder 1 and the lens holder 2 are firmly bonded. For this reason, it is preferable that the lens holder 2 is made of a material that transmits ultraviolet rays so that the adhesive 22 applied to the gap between the lens holder 1 and the lens holder 2 can also be cured. Polyolefin resins, polycarbonate resins, and the like are suitable as materials for forming the lens holder 2 because they can transmit ultraviolet rays, are inexpensive, and have stable physical properties. The lens holder 1 is made of a material that does not transmit visible light and ultraviolet light.

  After adjusting the optical axis of the objective lens 41 by the procedure described above, the adhesive 22 is cured by irradiating the adhesive 22 with ultraviolet rays, and the lens holder 2 is fixed to the lens holder 1. As a result, the adhesive 22 does not harden during adjustment of the optical axis of the objective lens 41, and adjustment does not become difficult. Further, since the ultraviolet curable resin can be cured in a relatively short time, the time required for adjustment is also shortened. Since the lens holder 2 transmits ultraviolet rays, the adhesive 22 can be cured uniformly. Moreover, since it is sufficient if there is a light source that emits ultraviolet rays, the capital investment is small. Of course, it goes without saying that there is an effect that the adhesive fixing time is short.

  Note that the objective lens fixed to the lens holder 2 preferably constitutes an optical system used for recording / reproduction of an optical disk having a relatively low recording density. The control accuracy of the light beam at the time of recording / reproducing with respect to the optical disc having a low recording density may be relatively lower than that of the optical disc having a high recording density. For this reason, the accuracy of the axis adjustment of the objective lens may be relatively lower than that of the optical disk having a high recording density, and the adjustment of the optical axis becomes easy.

  As shown in FIG. 3, in order to make a light beam of a desired size incident on the objective lens 34, the lens holder 1 defines the path of the light beam incident on the objective lens 34 so as to define the opening 1h. An opening restricting portion 14 protruding inside the through hole is provided. The opening limiting portion 14 is also made of a material that does not transmit visible light and ultraviolet light.

  On the other hand, when the lens holder 2 is made of a material that transmits ultraviolet rays, the lens holder 2 also transmits visible light. Therefore, it becomes difficult to obtain a desired numerical aperture (NA) by making a light beam having a desired size incident on the objective lens 41. In the present application, the objective lens unit 10 includes the aperture limiting unit 3. Hereinafter, the opening limiting portion 3 will be described in detail with reference to FIG.

  FIG. 4 is an enlarged cross-sectional view of the lens unit 10. As shown in FIG. 4, the lens holder 2 has a first opening 2b and a second opening 2a, and has a through hole defined by an inner surface 2f. The objective lens 41 is supported by the lens holder 2 so as to close the first opening 2b, and light that has passed through the through hole from the second opening 2a enters the objective lens 41. The opening restricting portion 3 has a shape protruding in the direction of the central axis 2c of the through hole along the circumferential direction of the inner surface 2f of the through hole. Thereby, the aperture limiting unit 3 defines the light diameter 2 h of the light beam incident on the objective lens 4. The central axis 2c of the through hole substantially coincides with the center 41c of the objective lens 41. The opening 2 h formed by the opening restriction unit 3 is set to be equal to or smaller than the effective aperture D that functions as the lens of the objective lens 41.

  As described above, the lens holder 2 transmits ultraviolet light and visible light. For this reason, when the aperture limiting portion 3 is integrally formed from the same material as the lens holder 2, the incident light is transmitted through the aperture limiting portion 3 as well, so that the light incident on the objective lens 41 is shielded and a predetermined light diameter is obtained. Cannot be specified. For this reason, a structure is provided in which light incident on the aperture limiting unit 3 from the second aperture 2 a of the aperture limiting unit 3 is guided in a direction away from the optical axis of the objective lens 41.

FIG. 5 shows an enlarged part of the cross section of the lens holder 2. As shown in FIG. 5, the cross section of the opening restricting portion 3 is trapezoidal, and the two restricting sides of the trapezoid make the opening restricting portion 3 a first ring-shaped inclined surface 3 a that protrudes into the through hole of the lens holder 2 and A second ring-shaped slope 3b is included. Is inclined with respect to the first ring-shaped inclined surface 3a and a second ring-shaped inclined surface 3b is first respective apertures 2 b and the second inner surface 2f so as to face the opening 2 a side. The side surface 3c of the opening limiting portion 3 is substantially parallel to the inner side surface 2f.

As shown in FIG. 5, the light 57 incident on the aperture limiting portion 3 out of the light incident on the second aperture 2a is transmitted from the first ring-shaped inclined surface 3a to the inside of the aperture limiting portion 3. At this time, the light 57 is refracted in the direction away from the optical axis 41c on the first ring-shaped inclined surface 3a. As a result, it is possible to prevent the light incident on the aperture limiting unit 3 from entering the objective lens 41. Therefore, as shown in FIG. 4, only the light having the light diameter 2 h defined by the aperture restriction unit 3 can be incident on the objective lens 41.

  The first ring-shaped inclined surface 3a and the second ring-shaped inclined surface 3b of the aperture restricting portion 3 constitute part of two spherical surfaces of the concave lens substantially coincident with the optical axis 4c, as indicated by a broken line in FIG. May be. Even if the first ring-shaped inclined surface 3a and the second ring-shaped inclined surface 3b have such a shape, the light 57 incident on the aperture limiting portion 3 can be refracted in a direction away from the optical axis 41c. Thereby, even if the aperture limiting unit 3 is made of a material that transmits visible light or ultraviolet light, the aperture limiting unit 3 can shield the light and allow light having a desired light diameter to enter the objective lens 41.

  In addition, since the aperture restricting portion 3 is provided inside the through hole through which light incident on the objective lens 41 of the lens holder 2 that supports the objective lens 41 passes, the aperture restricting portion 3 is disposed close to the objective lens 41. Thus, the deviation between the center of the aperture limiting portion 3 and the optical axis of the objective lens 41 can be reduced. Further, even when the inclination of the objective lens 41 with respect to the lens holder 1 is adjusted, the adjustment of the inclination is performed by the entire lens unit including the objective lens 41 and the lens holder 2. For this reason, the aperture limiter 3 always determines the light diameter of the light incident on the objective lens 41 without causing a shift between the center of the aperture limiter 3 and the optical axis of the objective lens 41. Therefore, an error in the diameter of light incident on the objective lens 41 can be minimized.

  In order to enhance the light shielding effect by the opening restriction unit 3, total reflection of light at the second ring-shaped inclined surface 3b may be used. Specifically, as shown in FIG. 6, the angle formed by the light 57 incident on the first ring-shaped inclined surface 3a and the normal line of the first ring-shaped inclined surface 3a is A1, and the ring-shaped inclined surface 3a enters the inside. The angle between the traveling light and the normal is A2. Further, the angle formed between the light incident on the second ring-shaped inclined surface 3b and the normal line is A4, and the angle formed between the light emitted from the second ring-shaped inclined surface 3b and the normal line is A3. Let n be the refractive index of the material constituting the aperture limiting portion 3.

  According to Snell's law, these angles satisfy the relationship of the following equations (1) and (2).

sin (A1) = n · sin (A2) (1)
A4 = A3 + (A1-A2) (2)

  The condition under which total reflection occurs on the second ring-shaped inclined surface 3b is expressed by Expression (3).

  n · sin (A4)> 1 (3)

  Therefore, the relationship of equation (4) is obtained by substituting equation (2) into equation (3).

  n · sin (A3 + (A1-A2))> 1 (4)

  In other words, if the angles A1 and A3 satisfy the relationship of the expressions (1) and (4), all the light incident on the first ring-shaped inclined surface 3a is refracted in a direction away from the optical axis 41c, and the objective is It can be prevented from entering the lens 41.

  By adopting such a structure, an unnecessary light beam does not enter the objective lens 41, so that an effect that the stray light component can be completely removed can be obtained.

  The opening restricting portion provided in the lens holder 2 may adopt a structure other than the structure shown in FIGS.

As shown in FIG. 7A, the opening limiting portion 63 provided in the lens holder 62 has two ring-shaped inclined surface portions 63d and 63d, a second ring-shaped inclined surface 63b, and a side surface 63c that are arranged concentrically. is doing. The ring-shaped slope portions 63d and 63e are inclined toward the second opening 2a, and the ring-shaped slope portion 63d and the ring-shaped slope portion 63e are discontinuous. The ring-shaped inclined surfaces 63d and 63e function as the first ring-shaped inclined surface 63a, and guide the light incident on the aperture limiting portion 63 in the direction away from the optical axis 41c as described with reference to FIG.

  By forming the first ring-shaped inclined surface 63a by the two discontinuous ring-shaped inclined surfaces 63d and 63e, the inclination angle with respect to the inner surface 63f of each of the ring-shaped inclined surfaces 63d and 63e is reduced, and the opening restricting portion 63 is formed. Can be refracted in a direction away from the optical axis 41c. In addition, the length L1 necessary for providing the ring-shaped slope portions 63d and 63e on the inner side surface 63f can be shortened as compared with the case where one ring-shaped slope inclined at the same angle is formed. Therefore, the length of the lens holder 62 in the through-hole direction can be shortened, which is suitable for realizing an optical information device having a small thickness.

As shown in FIG. 7B, the opening limiting portion 65 provided in the lens holder 64 includes a ring-shaped diffraction grating 65a, a second ring-shaped inclined surface 65b, and a side surface 65c provided on the second opening 2a side. Yes. The ring-shaped diffraction grating 65a can refract light incident on the aperture limiting portion 65 in a direction away from the optical axis 41c. The diffraction grating 65a can set the diffraction direction of light by an uneven pattern. The length L2 required for providing the diffraction grating 65a on the inner side surface 63f can be shortened compared with the case where the first ring-shaped slope is formed. Therefore, the length of the lens holder 64 in the through hole direction can be shortened, which is suitable for realizing an optical information device with a small thickness.

  The opening restricting portion 3 shown in FIG. 5 includes the first ring-shaped inclined surface 3a and the second ring-shaped inclined surface 3b, but may include only one of the inclined surfaces. The opening limiting portion 67 provided in the lens holder 66 shown in FIG. 7C includes a vertical surface 67a, a second ring-shaped inclined surface 67b, and a side surface 67c. The vertical surface 67a is perpendicular to the inner surface 67f, and when light 57 is incident, no light refraction occurs at the vertical surface 67a. However, by reducing the inclination angle of the second ring-shaped inclined surface 67b with respect to the inner surface 67f, the light 57 can be refracted away from the optical axis 41c on the second ring-shaped inclined surface 67b.

  In this case, as shown in FIG. 7C, when the angle formed by the direction in which the light 57 is incident and the normal line of the second ring-shaped inclined surface 67b is A3, the light 57 is the second if the equation (5) is satisfied. It is possible to prevent the light from being totally reflected on the ring-shaped inclined surface 67 b and entering the objective lens 41.

  n · sin (A3)> 1 (5)

  The opening limiting portion 69 provided in the lens holder 68 shown in FIG. 7D includes a first ring-shaped inclined surface 69a, a vertical surface 69b, and a side surface 69c. The opening limiting portion 69 can refract the light 57 in the direction away from the optical axis 41c by the first ring-shaped inclined surface 69a.

  The cross-sectional shape of the opening limiting portion may be configured by a curve. The opening limiting portion 72 provided in the lens holder 71 shown in FIG. 7E has a shape including a part of an ellipse protruding toward the central axis in a cross section passing through the central axis of the through hole. The aperture limiting portion 72 having such a shape can also refract the light 57 in the direction away from the optical axis 41c. The lens holder 71 having such a shape can be easily molded by a method such as injection molding, and the manufacturing cost of the lens holder 71 can be reduced.

The opening limiting portion described so far can be formed integrally with the lens holder 71 and has a structure that can be manufactured at low cost. However, if it is desired to shield light reliably, a light shielding surface may be provided at the opening limiting portion. As shown in FIG. 7F, the opening limiting portion 74 provided in the lens holder 73 is a ring-shaped member formed of generally vertical surfaces 74a and 74 and a side surface 74c protruding toward the optical axis 41c in the inner side surface 74f. It has a protruding shape. A ring-shaped shielding surface 75 is provided on the surface 74a facing the second opening 2a. The shielding surface 75 may be one surface of a ring-shaped sheet made of a resin containing black paint or graphite, or a colored resin, or the entire opening restricting portion 74 may be a resin containing black paint or graphite or colored. You may form with resin. A scattering surface that scatters light may be provided instead of the shielding surface 75 that shields light.

  Since the structural member different from the lens holder 2 is used, the manufacturing cost is somewhat increased, but the light shielding effect is high, and unnecessary light can be shielded more reliably.

  In the present embodiment, the lens unit is configured by the lens holder and the objective lens, but the lens unit may further include another optical element.

  For example, as shown in FIG. 7G, the lens unit 80 includes an objective lens 41, a lens holder 83, an opening limiting portion 82 provided in the lens holder, and an optical element 84.

  The opening restricting portion 82 may be any of the opening restricting portions having various structures described so far. Various optical elements such as a diffraction lens can be used for the optical element 84. Since the lens holder 83 transmits ultraviolet rays, the lens holder 83 and the optical element 84 can be bonded with an ultraviolet curable resin. For this reason, after appropriately adjusting the tilt and position of the objective lens 41, the aperture restricting portion 82, and the optical element 84, as described above, the ultraviolet light is irradiated and the optical element 84 is fixed to the lens holder 83, whereby the light is obtained. An optical unit whose axis is adjusted can be obtained.

  Next, the design of the optical system in the present embodiment will be described with reference to FIGS. The optical pickup 101 corresponds to optical disks 32, 35, and 46 having three different recording densities, and the optical disks 32, 35, and 46 are, for example, DVD, BD, and CD.

  In the recording / reproducing operation for a plurality of optical disks having different recording densities, the control accuracy is different. In general, high control accuracy is not required for recording / reproduction of an optical disc having a low recording density, but since the recording density is low, the moving range of the objective lens is required to be large. On the other hand, in the recording / reproduction of an optical disc having a high recording density, high control accuracy is required, but the movement range of the objective lens may be narrow. For example, since the recording density differs by about 40 times between a BD that is a high recording density optical disc and a CD that is a low recording density optical disc, the control accuracy and the movement range of the objective lens are also greatly different.

  For this reason, a relatively large shape distortion is allowed for a disk with a low recording density. When a disk with a low recording density is loaded in an optical information device and rotated by a spindle motor, the recording surface is deformed due to the distortion of the disk shape. The position changes up and down. In other words, it causes “blurring”. The dynamic range of the focus error signal must be large in order to reliably start focus control for a disk with large surface wobbling. Specifically, as shown in FIG. 8, it is desirable that the distance between the defocus point A at which the focus error signal is maximum and the focus point B at which the focus error signal is minimum is wide.

  On the other hand, in a high recording density optical disc, a condensing spot formed on the recording surface of the optical disc is small and the focal depth is shallow. Therefore, it is necessary to perform the focus control with higher accuracy, the interval between the defocus points A and B in FIG. 8 is narrow, and the detection sensitivity between the points AB must be high.

  In this embodiment, in order to cope with such a problem, an optical system corresponding to each optical disk is designed as follows.

  Specifically, the defocus detection range of the focus error signal obtained by irradiating the optical disk with the light beam 57 or the light beam 58 having a wavelength longer than that of the light beam 56 and detecting the reflected light with a photodetector is as follows. The optical system through which the light beams 56, 57, and 58 are transmitted is designed so that it is wider than the defocus detection range of the focus error signal obtained by irradiating the optical disk with the beam 56 and detecting the reflected light by the photodetector. .

  Preferably, the focal length f1 of the objective lens 34 is 1 mm to 1.8 mm, and the focal length fC1 of the collimating lens 33 is 14 mm to 30 mm. Further, the focal length f2 of the objective lens 41 is set to 2 mm to 3 mm, and the focal length fC2 of the collimating lens 39 is set to 10 mm to 20 mm.

  Further, within these focal length ranges, the first magnification obtained by dividing the focal length fC1 of the collimating lens 33 by the focal length f1 of the objective lens 34 is used, and the focal length fC2 of the collimating lens 39 is used as the second objective lens 41. Set larger than the second magnification divided by the focal length. That is, the focal lengths of these lenses are set so as to satisfy the relationship of the following formula (6).

  fC1 / f1> fC2 / f2 (6)

  Further, in order to satisfy the relationship of Expression (6), the focal length f2 of the objective lens 41 is made longer than the focal length f1 of the objective lens 34, or the focal length of the collimating lens 39 is made longer than the focal length fC1 of the collimating lens 33. It is preferable to shorten fC2.

  Thus, by selecting the focal lengths of the objective lenses 34 and 41 and the collimating lenses 33 and 39, high-precision focus control can be realized when recording and reproducing the high-density optical disk 35. Further, when recording / reproducing optical disks 32 and 46 having a low recording density, the defocus detection sensitivity can be lowered and the defocus detection range can be widened. For this reason, even when the surface shake of the rotating optical disk is large, the focus control can be reliably started.

  In particular, the relay lens 44 has a convex lens action, and the angle at which the light source 43a is viewed from the opening of the objective lens 41, that is, the numerical aperture (NA) on the light source side is converted from a large NA near the light source to an NA on the collimator lens 39 side. Accordingly, in this embodiment, it is possible to obtain the effect of making the defocus detection range the widest by making the magnification with the infrared light having the longest wavelength the smallest, making the defocus detection sensitivity low.

  A focus error signal obtained by the optical pickup having the optical system designed as described above is schematically shown below. FIG. 9 shows a focus error signal obtained when blue light is emitted from the light source 31 to the BD. FIG. 10 is a focus error signal obtained when the DVD is irradiated with red light from the light source 37a. FIG. 11 shows a focus error signal obtained when infrared light is emitted from the light source 43a to the CD.

  9 to 11, the horizontal axis indicates the defocus amount, that is, the distance between the recording surface and the convergence spot in the optical axis direction (focus direction), and the vertical axis indicates the intensity of the focus error signal.

  As shown in FIG. 9, in the BD focus error signal, the dynamic range, that is, the interval of the defocus amount at which the focus error signal intensity is maximized and minimized is set to about 2 μm. Further, as shown in FIG. 10, in the DVD focus error signal, the defocus amount interval at which the dynamic range, that is, the focus error signal intensity is maximum and minimum, is set to about 4 μm.

  This setting can be realized by setting the relationship between the focal lengths of the objective lens and the collimating lens, that is, the magnification. As a result, a focus error signal with high sensitivity to BD can be obtained, and high-precision focus control can be realized.

  At this time, as shown in FIG. 11, in the CD focus error signal, the dynamic range, that is, the defocus amount interval at which the focus error signal intensity becomes maximum and minimum, that is, the defocus detection range, is about 6 μm. This is the effect that the magnification is lowered from that of the DVD by the relay lens. In this way, it is possible to stably start the focus control even for a CD having a large surface shake.

  It should be noted that defocus detection sensitivity in infrared light can be reduced and defocus detection can be achieved by designing the focal length of the objective lens 41 in infrared light to be longer than the focal length of the objective lens 41 in red light. The effect of widening the range can be obtained.

(Second Embodiment)
In an optical pickup provided with a plurality of objective lenses, it is necessary to provide a plurality of through holes serving as light beam paths in the lens holder. In particular, in order to perform recording / reproduction with respect to an optical disc having a high recording density, it is necessary to use an objective lens having a large numerical aperture. For this reason, a through-hole also becomes large. Since such a lens holder has a large through hole, the rigidity is low, and the lens holder is likely to resonate at a predetermined frequency. The optical pickup of this embodiment includes an objective lens driving device having a structure that suppresses deterioration of servo performance due to resonance of the lens holder.

  12 and 13 are a perspective view and an exploded perspective view showing the objective lens driving device of the optical pickup according to the present embodiment. As in the first embodiment, arrows F, T, and Y indicate a focusing direction, a tracking direction, and a tangential direction of an optical disc (not shown), respectively. An arrow R indicates a tilt direction that is a rotation direction around the Y axis. The focusing direction F, the tracking direction T, and the direction Y are orthogonal to each other, and correspond to the directions of the coordinate axes in the three-dimensional orthogonal coordinates.

  The objective lens driving device 102 according to this embodiment includes a movable body 251. The movable body 251 includes an objective lens 201, an objective lens 202, a lens holder 203, a first print coil 204, a second print coil 205, and a terminal board 208.

  The lens holder 203 is made of resin or the like and supports the objective lens 201 and the objective lens 202. The objective lens 201 is used to perform recording / reproduction with respect to an optical disc having a low recording density such as a CD or a DVD. The objective lens 202 is used for recording / reproducing with respect to an optical disc having a high recording density such as a BD. A first printed coil 204 and a second printed coil 205 are attached to two side surfaces parallel to the direction Y in the lens holder 3, and a terminal plate 208 is attached to each of the two side surfaces parallel to the tracking direction T. It has been.

  Each of the first printed coil 204 and the second printed coil 205 is a printed coil in which a coil structure is formed by spirally attaching a conductive material around an axis parallel to the direction Y on the substrate.

  In the first printed coil 204, the first focusing coil portion 204a and the first tracking coil portion 204b are arranged and formed along the tracking direction T. Further, in the second printed coil 205, the second focusing coil portion 205a and the second tracking coil portion 205b are arranged and formed along the tracking direction T, respectively.

  The first focusing coil portion 204a and the second focusing coil portion 5a are located at a position shifted by an equal distance in the opposite direction from each other about the plane perpendicular to the tracking direction T including the direction Y and along the direction Y. It is arranged at a separated position. The first tracking coil unit 204b and the second tracking coil unit 205b are also arranged so as to satisfy the same relationship. Therefore, the first printed coil 204 and the second printed coil 205 can satisfy the above-described relationship by using the same component and arranging them at rotationally symmetric positions with respect to the direction Y.

  Both terminals of the first focusing coil section 204a and both terminals of the second focusing coil section 205a are independently connected to a control circuit (not shown) through a terminal plate 208 and a wire 209, respectively. The first tracking coil unit 204b and the second tracking coil 205b are connected in series with each other, and are connected to the control circuit through the terminal plate 208 and the wire 209.

  The optical pickup 102 further includes a first magnet 206 and a second magnet 207 for driving the movable body 251. Both the first magnet 206 and the second magnet 207 are magnetized differently in four regions with two lines of the focusing direction F and the tracking direction T as boundaries.

  The first magnet 206 faces the first printed coil 204 at a position where the center line 204c of the focusing coil part 204a of the first printed coil 204 and the center line 204d of the tracking coil part 204b coincide with the boundary line of the magnetic pole. And are fixed to the yoke 210. Similarly, the second magnet 207 is arranged such that the center line 205c of the focusing coil part 205a of the second print coil 205 and the center line 205d of the tracking coil part 205b coincide with the boundary lines of the magnetic poles. And is fixed to the yoke 209.

  The materials, shapes, magnetization patterns and magnetization strengths of the first magnet 206 and the second magnet 207 are preferably all equal, and the magnetic fields generated by the first magnet 206 and the second magnet 207 are substantially equal.

  A total of six terminals including two terminals of the first focusing coil unit 204a, two terminals of the second focusing coil unit 205a, and the tracking coil unit 204b and the tracking coil unit 205b connected in series are six via the terminal plate 208. The wire 209 is connected to the distal end side of the wire 209. The proximal end side of the wire 209 is fixed to the substrate 213 through the suspension holder 212. Further, the yoke 210, the suspension holder 212, and the substrate 213 are fixed to the base 211. The wire 209 is made of an elastic metal material such as beryllium copper or phosphor bronze, and a wire or rod having a cross-sectional shape such as a circle, a polygon, or an ellipse is used. The support center of the wire 209 is set so as to substantially coincide with the center of gravity of the movable body.

  The objective lens 201 and the objective lens 202 are arranged on the lens holder 203 along the direction Y. The objective lens 201 is disposed on the proximal end side of the wire 209 from the support center of the wire 209, and the objective lens 202 is disposed on the distal end side of the wire 209 from the support center of the wire 209.

  Further, the first printed coil 204 and the first magnet 206 are disposed on the proximal end side of the wire 209, and the second printed coil 205 and the second magnet 207 are disposed on the distal end side of the wire 209. That is, in the direction Y, the first printed coil 204 and the first magnet 206 are arranged on the objective lens 201 side, and the second printed coil 205 and the second magnet 207 are arranged on the objective lens 202 side.

  FIG. 14 shows a cross section of the lens holder 203 in a plane parallel to the direction Y. The objective lens 201 and the objective lens 202 have respective optical axes K1 and K2. Through holes for securing optical paths of light beams that pass through the objective lenses are arranged along the optical axes K1 and K2 at positions corresponding to the objective lenses 201 and 202 of the lens holder 203. Yes.

  The inventor of the present application has made various studies on the rigidity and resonance of the lens holder. As a result, it was found that when the through-hole formed in the lens holder becomes large, the rigidity of the lens holder may decrease, but the important factor for the deterioration of the servo performance is the resonance frequency. Further, it has been found that the resonance frequency varies depending on the distance p between the optical axis K1 and the optical axis K2, and the deterioration of the servo performance can be suppressed by setting the distance p to an appropriate value.

  FIG. 15 shows the relationship between the distance p between the optical axis K1 and the optical axis K2 and the amount of phase delay that occurs in servo control due to resonance. As shown in FIG. 15, the shorter the distance, the smaller the phase delay amount. If the distance p is reduced, the rigidity of the lens holder is further reduced, so that the adverse effect due to resonance is likely to increase. However, the phase delay is not due to the rigidity itself but depends on the resonance frequency.

  If the amount of phase delay is 10 degrees or less, the servo control characteristics do not deteriorate significantly, and the control does not become unstable. Therefore, as shown in FIG. 15, it is preferable to set the distance p between the optical axis K1 and the optical axis K2 to 5 mm or less. By setting the distance p to 5 mm or less, it is possible to suppress the occurrence of a phase delay in servo control due to resonance, and to reduce the amount of phase delay.

  From the viewpoint of suppressing an adverse effect due to resonance, an effect can be obtained if the distance p is 5 mm or less. The lower limit value of the preferable value of the distance p depends on the diameters of the objective lenses 201 and 202.

  The light beam is emitted from an optical block (not shown) arranged below the base 211 shown in FIG. The deviation between the optical axis of the light beam and the optical axis of the objective lens usually needs to be 10% or less of the diameter in order to suppress deterioration of the recording / reproducing signal. The preferred distance that the objective lens moves in the tracking direction in order to follow the track of the optical disk is 0.2 mm. From these points, the effective diameter of the objective lens is preferably about 2 mm. Further, it is necessary to secure a minimum width of 0.2 mm as the width of the flat portion for positioning formed around the objective lens. Further, the minimum clearance of 0.1 mm or more is required as a gap between the two objective lenses.

  From these factors, the distance p is preferably 2.5 mm or more. That is, the distance p is preferably 2.5 mm or more and 5 mm or less. The distance p is more preferably not less than 3.4 mm and not more than 3.8 mm. By setting the distance p in this range, the amount of phase delay of servo control due to resonance becomes about 5 deg, which is the same as the characteristic when there is no resonance. Characteristics can be obtained.

  In the objective lens driving device, when a current is passed through the focusing coil portion 204a of the first printed coil 204 and the focusing coil portion 205a of the second printed coil 205, the first magnet 206 and the second magnet 720 are interposed. Each generates an electromagnetic force and is driven in the focusing direction F.

  FIG. 16 shows a displacement frequency response characteristic in the focusing direction F of the lens holder 203 with respect to the current value passed through the focusing coil section 204a. Also. FIG. 17 shows a displacement frequency response characteristic of the lens holder 203 in the focusing direction F with respect to the phase delay amount of servo control. As shown in FIG. 16, the current value decreases as the displacement frequency increases, but there is almost no disturbance due to the frequency. As shown in FIG. 17, the amount of phase delay is approximately 5 degrees or less in the region from several hundred Hz to 10,000 Hz, and almost no phase delay occurs. This indicates that there is no phase delay in the focus control and that good control is realized. It also shows that control is not unstable due to phase delay and that stable control is realized.

  FIG. 18 schematically shows how resonance occurs in the conventional lens holder 114 including the objective lenses 116 and 117. In the conventional objective lens driving device, the distance between the two objective lenses is about 6 mm. 19 and 20 show a displacement frequency response characteristic in the focusing direction F of the lens holder with respect to the current value and a displacement frequency response characteristic in the focusing direction F of the lens holder with respect to the phase delay amount of servo control in the conventional objective lens driving device. Is shown. As shown in FIG. 19, the current value rapidly decreases at several tens of thousands of Hz. This is due to the resonance of the lens holder. As shown in FIG. 20, the amount of phase lag increases around tens of thousands of Hz due to resonance. Due to this influence, the amount of phase delay is large even in the vicinity of 10,000 Hz.

  As described above, according to the present embodiment, the resonance frequency of the lens holder can be appropriately controlled by reducing the distance between the two objective lenses, and the phase delay amount in the servo control can be reduced. . Therefore, according to the objective lens driving device of the present embodiment, it is possible to stably realize highly accurate servo control.

  The objective lens driving device of this embodiment can be suitably used as the objective lens driving device 45 in the optical pickup of the first embodiment. Thereby, in addition to the effect of 1st Embodiment, the optical pick-up which show | plays the effect of this embodiment is implement | achieved.

(Third embodiment)
In the present embodiment, an objective lens driving device having a structure suitable for realizing the distance between the two objective lenses described in the second embodiment will be described.

  21 and 22 are a plan view and an exploded perspective view showing the configuration of the objective lens driving device 103 according to the present embodiment. The direction T, the direction Y, and the direction F shown in FIGS. 21 and 22 indicate the focusing direction tracking direction and the tangential direction of the optical disc as in the second embodiment.

  The objective lens driving device 103 includes a movable body including an objective lens 301, an objective lens 302, a lens holder 303, focusing coils 304a to 304d, and tracking coils 305a and 305b.

  The lens holder 303 is made of resin and supports the objective lens 301 and the objective lens 302. The objective lens 301 is used for recording and reproduction of a low recording density optical disc such as a CD or a DVD. The objective lens 302 is used for recording / reproduction of a high recording density optical disc such as a BD.

  Focusing coils 304a to 304d and tracking coils 305a and 305b are attached to two side surfaces parallel to the tracking direction T in the lens holder 3, and a terminal plate 308 is attached to two side surfaces parallel to the direction Y. . The focusing coils 304a and 304c are connected in series, and both terminals thereof are connected to a control circuit (not shown) through the terminal plate 308, the wire 309, and the substrate 313. Similarly, the focusing coils 304b and 304d are connected in series, and both terminals are connected to a control circuit (not shown) through the terminal plate 308, the wire 309, and the substrate 313.

  The tracking coil 305a and the tracking coil 305b are connected in series to each other and connected to a control circuit (not shown) through the terminal plate 308, the wire 309, and the substrate 313.

  In order to drive the movable body, the objective lens driving device further includes a first magnet 306 and a second magnet 307. Both the first magnet 306 and the second magnet 7 are magnetized in a multipolar manner in a region divided by the lines corresponding to the focusing coils 304a to 304d and the tracking coils 305a and 305b. It is fixed to.

  The proximal end side of the wire 309 is fixed to the substrate 313 through the suspension holder 312. Further, the yoke 310, the suspension holder 312, and the substrate 313 are fixed to the base 311. The wire 309 is made of an elastic metal material such as beryllium copper or phosphor bronze, and a wire having a cross-sectional shape such as a circle, a polygon, or an ellipse, and h is a rod. The support center of the wire 309 is set so as to substantially coincide with the center of gravity of the movable body.

  The objective lens 301 and the objective lens 302 are arranged on the lens holder 303 along the direction Y. The objective lens 301 is closer to the base end side of the wire 309 than the support center of the wire 309, and the objective lens 302 is a support center of the wire 309. The wire 309 is installed on the tip side.

  FIG. 23 is a side view of the lens holder 314, and FIG. 24 shows a cross section taken along the line AA in FIG. 21 of the lens holder 303. As shown in FIGS. 22 and 24, a spherical concave surface portion 3a is formed in a portion of the lens holder 303 where the objective lens 301 is mounted, and the objective lens 301 has a spherical convex surface portion 314a. The lens unit mounted on 314 is disposed on the spherical concave surface portion 303 a of the lens holder 303. Therefore, as described in the first embodiment, the objective lens 301 is made independent of the objective lens 302 by sliding the spherical concave surface portion 303a of the lens holder 303 and the spherical convex surface portion 314a of the tilt holder 314 in contact with each other. It is possible to adjust the angle.

  As shown in FIGS. 23 and 24, the lens holder 314 has a flat side surface (D-cut surface) 314b at a position close to the objective lens 302. Moreover, it has a notch 314c in which a part of the spherical surface is notched at a position symmetrical to the side surface 314b with respect to the optical axis of the objective lens 301.

  The lens holder 303 has a projection 303b formed around the objective lens 302 and the objective lens 301. Preferably, a collision prevention material made of polyurethane resin is applied to the upper surface of the projection 303b. This prevents the objective lens 302 and the objective lens 301 from directly colliding with the optical disc (not shown). As shown in FIG. 25, the protrusion 303b is formed at a position other than the outer peripheral side of the optical disc (not shown).

  According to this embodiment, the two objective lenses are arranged adjacent to each other on the lens holder, and the objective lens 301 is fixed to the lens holder 3 via the lens holder 314. Since a flat side surface is provided at least at a position close to the objective lens 302 of the lens holder 314, the objective lens 301 and the objective lens 302 can be arranged closest to each other.

  Therefore, since the distance between the two lenses can be reduced, the optical head can be miniaturized without creating a useless space in the optical arrangement of the optical head.

  In addition, as described in the second embodiment, by realizing an arrangement in which the optical axes of the two objective lenses are close to each other, the interval between the two through holes serving as the optical paths of the two objective lenses can be reduced. The entire movable part can be reduced in size, and adverse effects due to resonance of the lens holder can be reduced, and a good displacement frequency response characteristic can be obtained. As a result, it is possible to realize an optical information device capable of ensuring stable servo performance and performing a stable recording / reproducing operation.

  In addition, as shown in FIG. 25, by arranging a flat side surface 314b on at least the outer peripheral side surface of the optical disc 15 of the lens holder 314, the outer peripheral cartridge is used when recording / reproducing is performed on the optical disc 315 included in the cartridge 316. The edge 316a and the lens holder 314 are not in contact with each other, and stable recording / reproduction can be realized.

  Similarly, since the protrusion 303b of the lens holder 303 is formed at a position other than the outer peripheral side, when recording / reproducing with respect to the optical disk 315 included in the cartridge 316, the outer peripheral cartridge edge 316a and the lens holder 314 come into contact with each other. Thus, stable recording and reproduction can be realized.

  Furthermore, as shown in FIGS. 23 and 24, the lens holder 314 has a spherical sliding surface 314a, and a part of the spherical surface is cut at a position symmetrical to the flat side surface with the optical axis of the objective lens 2 as the center. A notched portion 314c is provided. For this reason, as shown in FIG. 24, the contact area between the lens holder 314 and the lens holder 303 can be symmetric about the optical axis, and when the lens holder 303 and the lens holder 314 are bonded with an adhesive, The amount of deformation due to heat and the conductivity of heat become symmetrical, and the reliability can be improved.

  As described above, the objective lens driving device of the present embodiment can be suitably combined with the second embodiment. Further, it may be combined with the first embodiment, or only this embodiment and the first embodiment may be combined.

(Fourth embodiment)
An embodiment of an optical information device according to the present invention will be described with reference to FIG.

  The optical information device 104 includes an optical pickup 402, an electric circuit 403, and a motor 404.

  The optical disks 407 to 409 have different recording densities. The operator selects one of the optical disks 407 to 409 and places the selected optical disk on the turntable 405. The placed optical disk is fixed to the turntable 405 by a clamper 406 and is rotationally driven by a motor 404.

  As the optical head 402, the optical pickup 101 described in the first embodiment or the optical pickup equipped with the objective lens driving devices 102 and 103 desired to be described in the second and third embodiments can be suitably used.

  The optical pickup 402 can be moved in the tracking direction by a driving mechanism 401 such as a traverse motor, and can jump to a desired track.

  The optical pickup 403 outputs a focus error signal and a tracking error signal to the electric circuit 403 corresponding to the positional relationship with the optical disks 407 to 409. In response to this signal, the electric circuit 403 sends a signal for finely moving the objective lens to the optical pickup 403. In response to this signal, the optical pickup 402 performs focus control and tracking control on the optical disks 407 to 409, and the optical pickup 104 reproduces information or records information.

  According to the present embodiment, since the optical pickup of the first embodiment or the objective lens driving device of the second and third embodiments is provided, the recording / reproducing operation of a plurality of optical disks having different recording densities can be performed with high accuracy. An optical information apparatus that can be stably performed can be realized.

(Fifth embodiment)
An embodiment of a computer according to the present invention will be described with reference to FIG.

  The computer 105 includes the same optical information device 501 as the optical information device 104 described in the fourth embodiment. The computer 105 further performs a calculation based on an input device 503 such as a keyboard, a mouse, and a touch panel for inputting information, information input from the input device 503, information read from the optical information device 501, and the like. A computing device 502 such as a computing device (CPU) is provided.

  Further, an output device 504 such as a cathode ray tube, a liquid crystal display device, or a printer that displays information such as a result calculated by the arithmetic device 502 is provided.

  Since the computer 105 includes the same optical information device 501 as the optical information device described in the fourth embodiment, video information, audio information, or data can be recorded on different types of optical discs, or recorded on the optical disc. When the information is read out, and the information is processed and edited, the recording / reproducing operation with respect to different optical disks can be stably performed with high accuracy.

(Sixth embodiment)
An embodiment of an optical disc player according to the present invention will be described with reference to FIG.

  The optical disc player 106 includes the same optical information device 601 as the optical information device 104 described in the fourth embodiment. The optical disc player 106 further includes a conversion device 602 such as a decoder that converts an information signal obtained from the optical information device 601 into an image. The optical disc player 106 may also be used as a car navigation system. Further, a display device 603 such as a liquid crystal monitor may be further provided.

(Seventh embodiment)
An embodiment of an optical disk recorder according to the present invention will be described with reference to FIG.

  The optical disc recorder 107 includes the same optical information device 701 as the optical information device 104 described in the fourth embodiment. In addition, a conversion device 702 such as an encoder that converts image information into information to be recorded on an optical disk by the optical information device 701 is further provided. A decoder 703 for converting an information signal obtained from the optical information device 701 into an image may be further provided. Further, an output device 704 such as a cathode ray tube, a liquid crystal display device, or a printer that displays information may be provided.

(Eighth embodiment)
An embodiment of an optical disk server according to the present invention will be described with reference to FIG.

  The optical disk server 108 includes the same optical information device 801 as the optical information device 104 described in the fourth embodiment. Further, the server 108 captures information to be recorded in the optical information device 801 and outputs information read by the optical information device 801 to the outside, such as an input device 805 such as a keyboard, a mouse, and a touch panel for inputting information. A wired or wireless input / output terminal 802 is provided. Thus, it functions as an optical disk server that exchanges information with a network, that is, a plurality of devices such as a computer, a telephone, and a TV tuner, and shares information with the plurality of devices. An output device 804 such as a cathode ray tube, a liquid crystal display device, or a printer for displaying information may be further provided. Also, by providing a changer (not shown) for taking a plurality of optical discs into and out of the optical information device 801, a large amount of information can be recorded and accumulated.

(Ninth embodiment)
An embodiment of a vehicle 109 according to the present invention will be described with reference to FIG.

  The vehicle 109 includes the same optical information device 901 as the optical information device 104 described in the fourth embodiment.

  The vehicle 109 includes a vehicle body 915 and a power generation unit 912 that generates power for driving the vehicle body 915. In addition, a fuel storage unit 911 that stores fuel to be supplied to the power generation unit 912 and / or a power source 910 is provided. By mounting the optical information device 901 on the vehicle 109 in this manner, information can be stably obtained from various types of optical disks or information can be recorded while being in a moving body. When the vehicle 109 is a train or a car, wheels 907 are further provided for traveling. In addition, a handle 916 for changing the traveling direction is provided.

  Furthermore, by providing the changer 902 and the optical disk storage 903, a large number of optical disks can be used easily. It is possible to reproduce video information from the optical disk by providing an arithmetic unit 908 for processing information obtained from the optical disk, a semiconductor memory 909 and a display device 905 for temporarily storing information. Further, by providing the amplifier 913 and the speaker 914, voice and music can be reproduced from the optical disc.

  In addition, by providing a position sensor such as GPS906, the current position and the traveling direction are displayed on the display device 905 together with the map information reproduced from the optical disc, and the traffic information and the route guidance information are uttered as sound from the speaker 914. Can do. Furthermore, by providing the wireless communication unit 904, information from the outside can be obtained and used in a complementary manner with the information on the optical disc.

  Although the output device and the input device are shown in the fourth to ninth embodiments, only the input terminal and the output terminal are provided, and the output device and the input device are the same as those in the devices of the fourth to ninth embodiments. It does not have to be provided.

  The present invention is suitably used for an optical information apparatus such as an optical disk apparatus that performs at least one of recording and reproduction with respect to various optical disks. In particular, it is suitably used for an optical information device such as an optical disk device having a plurality of objective lenses.

1 is a schematic side view showing a first embodiment of an optical pickup according to the present invention. 1 is a schematic perspective view showing a first embodiment of an optical pickup according to the present invention. 2 shows a cross section of a movable portion of an objective lens driving device used in the optical pickup of FIG. It is an expanded sectional view of the lens unit used for the optical pick-up of FIG. It is sectional drawing which expands and shows a part of lens holder used for the optical pick-up of FIG. It is a figure explaining the optical path of the light which injects into the opening restriction | limiting part of a lens holder. It is sectional drawing which shows the other form of the opening restriction | limiting part of a lens holder. It is sectional drawing which shows the other form of the opening restriction | limiting part of a lens holder. It is sectional drawing which shows the other form of the opening restriction | limiting part of a lens holder. It is sectional drawing which shows the other form of the opening restriction | limiting part of a lens holder. It is sectional drawing which shows the other form of the opening restriction | limiting part of a lens holder. It is sectional drawing which shows the other form of the opening restriction | limiting part of a lens holder. It is sectional drawing which shows the other form of a lens unit. It is a figure which shows an example of a focus error signal. In this embodiment, it is a figure which shows the focus error signal obtained from the optical system for BD. In this embodiment, it is a figure which shows the focus error signal obtained from the optical system for DVD. In this embodiment, it is a figure which shows the focus error signal obtained from the optical system for CD. It is a perspective view which shows the objective lens drive device by 2nd Embodiment. It is a disassembled perspective view which shows the objective lens drive device by 2nd Embodiment. It is sectional drawing of the lens holder of the objective lens drive device of FIG. It is a figure which shows the relationship between the distance between optical axes, and the delay amount of a servo control phase. It is a figure which shows the displacement frequency response characteristic to the focusing direction of a lens holder with respect to the electric current value which flows into a focusing coil in this embodiment. It is a figure which shows the displacement frequency response characteristic to the focusing direction of a lens holder with respect to the phase delay amount of servo control in this embodiment. It is a figure which shows typically the mode of resonance of the conventional lens holder. It is a figure which shows the displacement frequency response characteristic to the focusing direction of a lens holder with respect to the electric current value which flows into a focusing coil in the conventional objective lens drive device. It is a figure which shows the displacement frequency response characteristic to the focusing direction of a lens holder with respect to the phase delay amount of the servo control in the conventional objective lens drive device. It is a top view which shows the structure of the objective lens drive device by 3rd Embodiment. It is a disassembled perspective view which shows the structure of the objective lens drive device by 3rd Embodiment. It is a side view of the lens holder of 3rd Embodiment. FIG. 22 shows a cross section taken along line AA in FIG. It is a figure which shows the positional relationship of the objective lens drive device of 3rd Embodiment, and an optical disk. It is a figure which shows the structure of the optical information apparatus by 4th Embodiment. It is a figure which shows the structure of the computer by 5th Embodiment. It is a figure which shows the structure of the optical disk player by 6th Embodiment. It is a figure which shows the structure of the optical disk recorder by 7th Embodiment. It is a figure which shows the structure of the server by 8th Embodiment. It is a figure which shows the structure of the vehicle by 9th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Lens holder 3 Opening restriction part 31, 37a, 43a Light source 34, 41 Objective lens 33, 39 Collimate lens 32, 35, 46 Optical disk 45 Objective lens drive device 56, 57, 58 Light beam

Claims (37)

A first light source;
An objective lens unit;
A support for holding the objective lens unit;
An actuator for driving the support;
A first photodetector;
With
The light emitted from the first light source is condensed on the data recording surface of the optical disk by the first objective lens of the objective lens unit, and the light reflected on the data recording surface is converted into an electrical signal by the photodetector. A pickup,
The objective lens unit includes a first objective lens,
A first lens holder for supporting the first objective lens;
With
The first lens holder is made of a material that transmits the light, has first and second openings, a through-hole through which light incident on the first objective lens passes, and a circumferential direction in the through-hole And an opening restriction portion protruding in the direction of the central axis of the through hole along
The aperture limiting unit is an optical pickup that guides light incident on the aperture limiting unit from the second opening in a direction away from the optical axis of the first objective lens. The optical pickup according to claim 1, wherein the first objective lens is supported so as to close the first opening. The optical pickup according to claim 1, wherein the first lens holder is made of a material that transmits ultraviolet rays. 2. The optical pickup according to claim 1, wherein the opening limiting portion has a first ring-shaped inclined surface inclined with respect to an inner surface of the through hole so as to face the first opening side. 2. The optical pickup according to claim 1, wherein the opening limiting portion has a second ring-shaped inclined surface that is inclined with respect to an inner surface of the through-hole so as to face the second opening side. The opening restricting portion includes a first ring-shaped inclined surface inclined with respect to an inner surface of the through hole so as to face the first opening side, and the penetrating surface facing the second opening side. The optical pickup according to claim 1, further comprising a second ring-shaped inclined surface inclined with respect to the inner surface of the hole. The angle formed between the light incident on the second ring-shaped slope and the normal line of the second ring-shaped slope is A1, and the light emitted from the second ring-shaped slope and the second ring-shaped slope. The angle between the normal line and the normal line is A2, the angle between the light incident on the second ring-shaped slope and the normal line of the first ring-shaped slope is A3, and the refractive index of the aperture limiting portion Where n is
sin (A1) = n · sin (A2)
And n · sin (A3 + (A1-A2))> 1
The optical pickup according to claim 5 , wherein the relationship is satisfied. The optical pickup according to claim 5, wherein the ring-shaped slope has two discontinuous ring-shaped slope portions arranged concentrically. 2. The optical pickup according to claim 1, wherein the opening restricting portion has a shape constituting a part of a concave lens having an axis coinciding with a central axis of the through hole. 2. The optical pickup according to claim 1, wherein a cross section of the opening limiting portion passing through a central axis of the through hole is a part of an ellipse protruding toward the central axis. 2. The optical pickup according to claim 1, wherein the opening limiting portion includes a diffraction grating provided on the first opening side. 2. The optical pickup according to claim 1, wherein the aperture limiting portion has a scattering surface that scatters a light beam provided on the first aperture side. 2. The optical pickup according to claim 1, wherein the opening restriction portion has a shielding surface that shields a light beam provided on the first opening side. The optical pickup according to claim 1, wherein the first lens holder of the objective lens unit is bonded to the support with an ultraviolet curable resin. Further comprising a second objective lens and the second light source does not share an optical system and an optical axis of said objective lens unit is configured, the support according to claim 14 which is a second lens holder for supporting the second objective lens Optical pickup. The optical pickup according to claim 15 , wherein an interval between the optical axis of the first objective lens and the optical axis of the second objective lens is 5 mm or less. The optical pickup according to claim 15 , wherein an interval between the optical axis of the first objective lens and the optical axis of the second objective lens is 2.5 mm or more and 5 mm or less. The optical pickup according to claim 15 , wherein the first objective lens and the second objective lens are disposed so as to be positioned in a tracking direction of the optical disc. The optical pickup according to claim 15 , wherein the first objective lens and the second objective lens are disposed so as to be positioned in a direction perpendicular to a tracking direction of the optical disc. The optical pickup according to claim 16 , wherein the first lens holder has a flat side surface at a position close to the second objective lens. The first lens holder optical pickup according to claim 16 or 20 having a flat side on the outside of the optical disc. Wherein the first objective lens is an optical pickup according to claim 19 for use in condensing the light of wavelength longer than the second objective lens 21. The first lens holder, the optical pickup according to any one of claims 19 22 having a cutout portion in the flat sides and symmetrical positions about the optical axis of the first objective lens. The apparatus further includes a protrusion protruding from the first lens holder and the second lens holder than the first objective lens and the second objective lens, and the protrusion is provided in a region other than the outer peripheral side of the optical disc. The optical pickup according to claim 15 . A second light source, a second detector, and a second objective lens;
The first light source emits light of a first wavelength;
The first objective lens condenses the light emitted from the first light source toward the recording surface of the first optical disc,
The first detector receives reflected light of the light condensed on the recording surface of the first optical disc, and outputs a detection signal;
The second light source emits light having a second wavelength shorter than the first wavelength;
The second objective lens condenses the light emitted from the second light source toward the recording surface of the second optical disc,
The second detector receives reflected light of the light collected on the recording surface of the second optical disc, and outputs a detection signal;
The focus detection range of the focus error signal generated based on the detection signal of the second detector is wider than the focus detection range of the focus error signal generated based on the detection signal of the second detector. Item 14. The optical pickup according to any one of Items 1 to 13 . A first collimating lens for reducing the divergence of the light emitted from the first light source;
A second collimating lens for reducing the divergence of the light emitted from the second light source;
Further comprising
The first magnification obtained by dividing the focal length of the first collimating lens by the focal length of the first objective lens divides the focal length of the second collimating lens by the focal length of the second objective lens. The optical pickup according to claim 25, which is smaller than the second magnification obtained by the following. The optical pickup according to claim 25 , wherein a focal length of the first objective lens is longer than a focal length of the second objective lens. A first collimating lens for reducing the divergence of the light emitted from the first light source;
A second collimating lens for reducing the divergence of the light emitted from the second light source;
Further comprising
The optical pickup according to claim 25 , wherein a focal length of the first collimating lens is shorter than a focal length of the second collimating lens. An optical pickup as defined in any of claims 14 to 28 ;
A motor for rotating the optical disk;
An electric circuit for controlling the optical pickup based on a signal obtained from at least the first photodetector of the optical pickup;
An optical information device. A computer comprising an optical information device as defined in claim 29 . An optical disc player comprising the optical information device defined in claim 29 . A car navigation system comprising the optical information device defined in claim 29 . An optical disk recorder comprising the optical information device defined in claim 29 . An optical disk server comprising the optical information device defined in claim 29 . A vehicle comprising the optical information device defined in claim 29 . An optical pickup assembly method as defined in claim 15 ,
A first step of adjusting the inclination of the entire first lens holder so that coma aberration on the recording surface of the optical disc is minimized when the light beam from the second light source is collected by the second objective lens; ,
Coma on the recording surface of the optical disc when the light beam from the first light source is condensed by the second objective lens in a state in which the inclination of the entire first lens holder adjusted in the first step is maintained. A second step of adjusting the inclination of the objective lens unit with respect to the first lens holder so that the
Method of assembling an optical pickup. The optical pickup further includes a third light source condensed by a second objective lens,
After the second step, the position of the third light source is set so that the coma aberration on the recording surface of the optical disc is minimized when the light beam from the third light source is collected by the second objective lens. The method of assembling an optical pickup according to claim 36 , further comprising a third step of adjusting a position in a direction perpendicular to the optical axis of the light beam.

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